The overall aim of the proposed investigation is to extend our studies of coercive family processes to the role of negative sibling interactions (1) within the family context and (2) in the prediction of adjustment difficulties in adolescence and early adulthood. There are three major goals to be achieved: first, the testing and refinement of a theoretically driven model of children at risk in which younger siblings of sisters and brothers who have already experienced problems in adjustment are hypothesized to be at significantly greater risk to develop similarly poor adjustment outcomes; second, the development of a conjoint model which links Patterson and his colleagues (Patterson, 1982, 1986;Patterson & Band, 1986, 1989; Patterson, Bank & Stoolmiller, 1990) unskilled parenting practices variables with sibling negative interaction variables in the prediction of poor adjustment outcomes; and third, tests of predictive validity using observation-based microsocial variables to predict both later adjustment outcomes and behaviors in a variety of contexts including parent-child and sibling-sibling relationships in the family context, sibling-peer interaction in naturalistic playground and problem-solving laboratory observation, and sibling-sibling interaction in a laboratory problem-solving task. The microsocial variables, negative intrusions to the target child (NIC), and negative reinforcement of the target child's coercive behavior (NRC) are microsocial variables based on Herrnstein's (1961;1970) matching law. The proposed study is an extension of the longitudinal Oregon Youth Study (OYS) to approximately 300 male and female siblings of the 206 boys targeted in the OYS. Home observations in the first and third waves of the OYS included these siblings, and data from the parents have been collected on a regular basis as well. In addition, the proposed project would gather archival information from schools and courts, and current and retrospective data from the siblings and their parents through interviews, questionnaires, and a sibling interaction task for 90 OYS boy-younger sibling dyas. Analysis include tests of a multiple indicator Sibling Amplifier model using structural equation modeling techniques in which it is hypothesized that Negative Sibling Interaction will account for unique variance, in addition to that explained by Unskilled Parenting Practices, in four adjustment areas, Antisocial and Internalizing Behaviors, School Difficulties, and Rejection by Peers. Latent growth modeling (LGM) will be used to test the effects of an older siblings' adjustment trajectories on the later adjustment of younger siblings. Finally, multiple regression techniques will be used to test the hypothesis specific microsocial (NIC and NRC) will significantly predict (1) rates of coercive behavior in families, (2) the likelihood of aggressive acts in the playground, and (3) current sibling interaction patterns in the lab risk.